The Collaborative International Dictionary of English v.0.48:

Steaminess \Steam"i*ness\ (-[i^]*n[e^]s), n.
   The quality or condition of being steamy; vaporousness;
   mistiness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

steaminess
    n 1: cloudiness resulting from haze or mist or vapor [syn:
         haziness, mistiness, steaminess, vaporousness,
         vapourousness]